U.S. patent application number 15/298683 was filed with the patent office on 2018-04-26 for system and method for preamble sequence transmission and reception to control network traffic.
The applicant listed for this patent is Gerhard SCHREIBER, Marcos TAVARES. Invention is credited to Gerhard SCHREIBER, Marcos TAVARES.
Application Number | 20180115998 15/298683 |
Document ID | / |
Family ID | 60201685 |
Filed Date | 2018-04-26 |
United States Patent
Application |
20180115998 |
Kind Code |
A1 |
SCHREIBER; Gerhard ; et
al. |
April 26, 2018 |
SYSTEM AND METHOD FOR PREAMBLE SEQUENCE TRANSMISSION AND RECEPTION
TO CONTROL NETWORK TRAFFIC
Abstract
The method includes generating a preamble sequence at a
transmitter, where the transmitter is capable of generating a first
type of preamble sequence and a second type of preamble sequence.
The transmitter transmits a request message to a receiver to
request network resources, where the request message including the
preamble sequence. The transmitter receives a feedback message from
the receiver. The transmitter controls the network data traffic
based on the feedback message. The method further includes
receiving, a receiver, a signal from the transmitter, the signal
including the preamble sequence. The receiver detects the preamble
sequence within the signal, where the receiver is capable of
detecting a first type of preamble sequence and a second type of
preamble sequence. The receiver identifies a request message within
the signal based on the detected preamble sequence, and controls
the network data traffic based on the identified request
message.
Inventors: |
SCHREIBER; Gerhard;
(Korntal-Muenchingen, DE) ; TAVARES; Marcos;
(Marlboro, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHREIBER; Gerhard
TAVARES; Marcos |
Korntal-Muenchingen
Marlboro |
NJ |
DE
US |
|
|
Family ID: |
60201685 |
Appl. No.: |
15/298683 |
Filed: |
October 20, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 88/08 20130101;
H04W 74/0833 20130101; H04W 88/02 20130101; H04L 5/0051 20130101;
H04L 5/0091 20130101; H04B 7/0811 20130101; H04L 27/2613
20130101 |
International
Class: |
H04W 74/08 20060101
H04W074/08; H04B 7/08 20060101 H04B007/08 |
Claims
1. A method of preamble transmission to control network data
traffic in a communication network, comprising: generating, by at
least one processor, a first preamble sequence, the at least one
processor being capable of generating a first type of preamble
sequence and a second type of preamble sequence; first
transmitting, by the least one processor, a first request message
to a receiver to request network resources, the first request
message including the first preamble sequence which is one of the
first type of preamble sequence and the second type of preamble
sequence; and receiving, by the at least one processor, a feedback
message from the receiver; and controlling, by the at least one
processor, the network data traffic of the communication network
based on the feedback message.
2. The method of claim 1, wherein the first request message
includes a first set of data payload packets associated with the
first request message, the controlling of the network data traffic
further including, second transmitting a second set of data payload
packets, using assigned network resources, following the reception
of the feedback message, the feedback message identifying the
assigned network resources.
3. The method of claim 1, wherein the first type of preamble
sequence is a cyclic-shifted Zadoff-Chu (ZC) root sequence, and the
second type of preamble sequence is a circular delay-Doppler
shifted M-root sequence.
4. The method of claim 1, further comprising: receiving, from the
receiver, indicator information indicating that the at least one
processor should use one of the first type of preamble sequence and
the second type of preamble sequence in order to generate the first
preamble sequence.
5. A method of preamble detection to control network traffic in a
communication network, comprising: receiving, by at least one
processor, a signal from a transmitter, the signal including a
first preamble sequence; detecting, by the at least one processor,
the first preamble sequence within the first signal, the at least
one processor being capable of detecting a first type of preamble
sequence and a second type of preamble sequence; identifying, by
the at least one processor, a first request message within the
first signal based on the detected first preamble sequence; and
controlling, by the at least one processor, the network data
traffic of the communication network based on the identified first
request message.
6. The method of claim 5, wherein the identifying of the first
request message further includes identifying a first set of data
payload packets within the first signal that is associated with the
first request message, the controlling of the network data traffic
further including, transmitting, to the transmitter, a feedback
message, the feedback message identifying assigned network
resources; and receiving, from the transmitter, a second set of
data payload packets using the assigned network resources.
7. The method of claim 5, wherein the first type of preamble
sequence is a cyclic-shifted Zadoff-Chu (ZC) root sequence, and the
second type of preamble sequence is a circular delay-Doppler
shifted M-root sequence.
8. The method of claim 7, wherein the detecting of the first
preamble sequence includes using a serial processing detection
including, removing a first cyclic prefix and a zero tail from the
first signal to make a modified first signal, transforming the
modified first signal in a first frequency domain signal,
correlating the first frequency domain signal with a
complex-conjugated, Fourier transformed root sequence to create a
first inverse Fourier-transform, and performing serial detection of
the first inverse Fourier-transform, using both a ZC root sequence
detection and a M-root sequence detection in series, in order to
detect the first preamble sequence.
9. The method of claim 7, wherein the detecting of the first
preamble sequence includes using a parallel processing detection
including, removing a first cyclic prefix and a zero tail from the
first signal to make a modified first signal, transforming the
modified first signal in a first frequency domain signal,
correlating the first frequency domain signal with a
complex-conjugated, Fourier transformed root sequence to create a
first inverse Fourier-transform, performing parallel detection of
the first inverse Fourier-transform, using both a ZC root sequence
detection and a M-root sequence detection in parallel, in order to
detect the first preamble sequence.
10. The method of claim 7, wherein the detecting of the first
preamble sequence includes a processing detection in a time domain
that is one of a serial processing detection and a parallel
processing detection, the processing detection in the time domain
including a direct correlation between the received signal and time
domain reference sequences.
11. At least a first network node in a communication network,
comprising: at least one processor, configured to, generate a first
preamble sequence, the at least one processor being capable of
generating a first type of preamble sequence and a second type of
preamble sequence, transmit a first request message to a receiver
to request network resources, the first request message including
the first preamble sequence which is one of the first type of
preamble sequence and the second type of preamble sequence, and
receive a feedback message from the receiver, and control the
network data traffic of the communication network based on the
feedback message.
12. The at least a first network node of claim 11, wherein the
first request message includes a first set of data payload packets
associated with the first request message, the at least one
processor controlling the network data traffic by being further
configured to, transmit a second set of data payload packets, using
assigned network resources, following the reception of the feedback
message, the feedback message identifying the assigned network
resources.
13. The at least a first network node of claim 11, wherein the
first type of preamble sequence is a cyclic-shifted Zadoff-Chu (ZC)
root sequence, and the second type of preamble sequence is a
circular delay-Doppler shifted M-root sequence.
14. The at least a first network node of claim 11, wherein the at
least one processor is further configured to, receive, from the
receiver, indicator information indicating that the at least one
processor should use one of the first type of preamble sequence and
the second type of preamble sequence in order to generate the first
preamble sequence.
15. At least a first network node in a communication network,
comprising: at least one processor, configured to, receive a signal
from a transmitter, the signal including a first preamble sequence,
detect the first preamble sequence within the first signal, the at
least one processor being capable of detecting a first type of
preamble sequence and a second type of preamble sequence, identify
a first request message within the first signal based on the
detected first preamble sequence, and control the network data
traffic of the communication network based on the identified first
request message.
16. The at least a first network node of claim 15, wherein the at
least one processor identifies the first request message by being
further configured to identify a first set of data payload packets
within the first signal that is associated with the first request
message, and the at least one processor controls the network data
traffic by being further configured to, transmit a feedback
message, the feedback message identifying assigned network
resources, and receive a second set of data payload packets using
the assigned network resources.
17. The at least a first network node of claim 15, wherein the
first type of preamble sequence is a cyclic-shifted Zadoff-Chu (ZC)
root sequence, and the second type of preamble sequence is a
circular delay-Doppler shifted M-root sequence.
18. The at least a first network node of claim 17, wherein the at
least one processor detects the first preamble sequence by using a
serial processing detection that includes the at least one
processor being configured to, remove a first cyclic prefix and a
zero tail from the first signal to make a modified first signal,
transform the modified first signal in a first frequency domain
signal, correlate the first frequency domain signal with a
complex-conjugated, Fourier transformed root sequence to create a
first inverse Fourier-transform, and perform serial detection of
the first inverse Fourier-transform, using both a ZC root sequence
detection and a M-root sequence detection in series, in order to
detect the first preamble sequence.
19. The at least a first network node of claim 17, wherein the at
least one processor detects the first preamble sequence by using a
parallel processing detection that includes the at least one
processor being configured to, remove a first cyclic prefix and a
zero tail from the first signal to make a modified first signal,
transform the modified first signal in a first frequency domain
signal, correlate the first frequency domain signal with a
complex-conjugated, Fourier transformed root sequence to create a
first inverse Fourier-transform, perform parallel detection of the
first inverse Fourier-transform, using both a ZC root sequence
detection and a M-root sequence detection in parallel, in order to
detect the first preamble sequence.
20. The at least a first network node of claim 17, wherein the at
least one processor detects the first preamble sequence by being
further configured to, perform a processing detection in a time
domain that is one of a serial processing detection and a parallel
processing detection, the processing detection in the time domain
including a direct correlation between the received signal and time
domain reference sequences.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] Example embodiments relate generally to a system and method
for using preamble sequencing at a transmitter and receiver to
control network traffic.
Related Art
[0002] FIG. 1 illustrates a conventional network 10. The network 10
includes an Internet Protocol (IP) Connectivity Access Network
(IP-CAN) 100 and an IP Packet Data Network (IP-PDN) 1001. The
IP-CAN 100 may include one or more evolved universal terrestrial
radio access network (E-UTRAN) Node B (eNB) 105 (i.e., base
station; for the purposes herein the terms base station and eNB may
be used interchangeably). For simplicity sake, only one eNB 105 is
shown in FIG. 1. The eNB 105 may be controlled by a controller (CO)
101, where the controller 101 may either exist within the eNB 105,
or be a separate entity (i.e., node) from the eNB 105. The CO 101
may control the functions of multiple eNBs 105. Although not shown,
the IP-PDN 1001 may include application or proxy servers, media
servers, email servers, etc.
[0003] The eNB 105 is capable of providing wireless resources and
radio coverage for one or more user equipments (UEs) 110. That is
to say, any number of UEs 110 may be connected (or attached) to the
eNB 105.
[0004] FIG. 2 illustrates a conventional E-UTRAN Node B (eNB) 105.
The eNB 105 generally includes: a memory 225; a processor 210; a
scheduler 215; wireless communication interfaces 220; radio link
control (RLC) buffers 230 for each bearer; and a backhaul interface
235. The processor 210 may consist of one or more core processing
units, either physically coupled together or distributed. The
processor 210 can control the function of eNB 105 (as described
herein), and is operatively coupled to the memory 225 and the
communication interfaces 220. While only one processor 210 is shown
in FIG. 2, it should be understood that multiple processors may be
included in a typical eNB 105. The functions performed by the
processor 210 may be implemented using hardware. Such hardware may
include one or more Central Processing Units (CPUs), digital signal
processors (DSPs), application-specific-integrated-circuits, field
programmable gate arrays (FPGAs) computers or the like. The term
processor, used throughout this document, may refer to any of these
example implementations, though the term is not limited to these
examples. With a Virtual Radio Access Network (VRAN) architecture
various functions eNB components may be distributed across multiple
processing circuits and multiple physical nodes within a VRAN
cloud.
[0005] The eNB 105 may include one or more cells or sectors serving
UEs 110 within individual geometric coverage sector areas. Each
cell individually may contain elements depicted in FIG. 2.
Throughout this document the terms eNB, cell or sector shall be
used interchangeably.
[0006] Still referring to FIG. 2, the wireless communication
interfaces 220 may include various interfaces including one or more
transmitters/receivers connected to one or more antennas to
transmit/receive wirelessly control and data signals to/from UEs
110. The backhaul interface 235 is the portion of eNB 105 that may
interface with other eNBs, or interface with other network elements
and/or RAN elements within IP-CAN 100. The scheduler 215 schedules
control and data communications that are to be transmitted and
received by the eNB 105 to and from UEs 110. The memory 225 may
buffer and store data that may be processed at eNB 105, transmitted
and received to and from eNB 105.
[0007] Scheduler 215 may make physical resource block (PRB)
allocation decisions. The PRB allocations may be based upon a
Quality of Service (QoS) Class Identifier (QCI), which represents
traffic priority hierarchy, for instance.
[0008] A random access channel (RACH) may enable user equipments
(UEs) 110 to perform tasks such as initially accessing the
communication network 10, uplink synchronization, handovers between
cells, and recovery from failed links. Therefore, an achievement of
an optimal random access performance through an efficient RACH
signature detection algorithm, and use of a correct configuration
of the RACH parameters, is crucial to optimizing performance of the
communication network.
[0009] FIG. 3 illustrates a conventional network controller 300.
The controller 300 may include: a processor 302, a memory 304, a
wireless interface 306 and a backhaul 308. The processor 302 of the
controller 300 may control the function of multiple eNBs 105 within
the IP-CAN 100 of the network 10.
[0010] FIG. 4 illustrates a conventional user equipment (UE) 100,
which may be a mobile device. In particular, the UE 100 may be a
cellphone, a laptop, a tablet, or any other type of user terminal
device. The UE 100 may include: a processor 154, a memory 150 and a
wireless interface 152.
[0011] Transmission of a random access (RA) preamble in an uplink
transmission is one of the first steps of a UE 110 to obtain access
to the network 10. Sets of signature sequences are ideally defined
in order to display acceptable auto-correlation and low cross
correlation, with a low susceptibility against impairments that
originate in time and frequency domain to guarantee low false-alarm
and miss-detection probabilities. To that end, Zadoff-Chu (ZC)
sequences have conventionally been implemented for radio access as
they are generally designed to show high robustness in
time-dispersive channels. However, the ZC sequences can experience
problems in channels that are simultaneously frequency-dispersive.
Currently, in the context of 5G networks, there is a high demand to
support data access for a large number of wireless devices (i.e., 1
million or more devices per square kilometer) within a single cell.
Important key performance parameters include latency and latencies
and reliability of these devices within the network 10. In radio
communication systems, specific reference signal sequences are
generally employed to enable reliable data transmission over the
air interface. Reference signal sequences normally do not contain
data, but are instead used to perform important tasks like an
initial setup for radio access, channel estimation and/or channel
quality assessment. Conventionally, industry standards define only
one sequence design for a specific task, which is the Zadoff-Chu
(ZC) sequences that may be employed for the physical random access
channel (PRACH).
[0012] Additionally, in scenarios involving massive connectivity,
mission critical applications and applications involving high
Doppler shifts (where UEs 110 may be traveling at relatively high
speeds, for example), legacy long-term evolution (LTE) PRACH
configurations may not be capable of fulfilling all necessary
performance requirements.
SUMMARY OF INVENTION
[0013] At least one example embodiment relates to a method of
preamble transmission to control network data traffic in a
communication network.
[0014] In one embodiment, the method includes generating, by at
least one processor, a first preamble sequence, the at least one
processor being capable of generating a first type of preamble
sequence and a second type of preamble sequence; first
transmitting, by the least one processor, a first request message
to a receiver to request network resources, the first request
message including the first preamble sequence which is one of the
first type of preamble sequence and the second type of preamble
sequence; and receiving, by the at least one processor, a feedback
message from the receiver; and controlling, by the at least one
processor, the network data traffic of the communication network
based on the feedback message.
[0015] In one embodiment, the first request message includes a
first set of data payload packets associated with the first request
message, the controlling of the network data traffic further
including, second transmitting a second set of data payload
packets, using assigned network resources, following the reception
of the feedback message, the feedback message identifying the
assigned network resources.
[0016] In one embodiment, the first type of preamble sequence is a
cyclic-shifted Zadoff-Chu (ZC) root sequence, and the second type
of preamble sequence is a circular delay-Doppler shifted M-root
sequence.
[0017] In one embodiment, the method further includes receiving,
from the receiver, indicator information indicating that the at
least one processor should use one of the first type of preamble
sequence and the second type of preamble sequence in order to
generate the first preamble sequence.
[0018] At least another example embodiment relates to a method of
preamble detection to control network traffic in a communication
network.
[0019] In one embodiment, the method includes receiving, by at
least one processor, a signal from a transmitter, the signal
including a first preamble sequence; detecting, by the at least one
processor, the first preamble sequence within the first signal, the
at least one processor being capable of detecting a first type of
preamble sequence and a second type of preamble sequence;
identifying, by the at least one processor, a first request message
within the first signal based on the detected first preamble
sequence; and controlling, by the at least one processor, the
network data traffic of the communication network based on the
identified first request message.
[0020] In one embodiment, the identifying of the first request
message further includes identifying a first set of data payload
packets within the first signal that is associated with the first
request message, the controlling of the network data traffic
further including, transmitting, to the transmitter, a feedback
message, the feedback message identifying assigned network
resources; and receiving, from the transmitter, a second set of
data payload packets using the assigned network resources.
[0021] In one embodiment, the first type of preamble sequence is a
cyclic-shifted Zadoff-Chu (ZC) root sequence, and the second type
of preamble sequence is a circular delay-Doppler shifted M-root
sequence.
[0022] In one embodiment, the detecting of the first preamble
sequence includes using a serial processing detection including,
removing a first cyclic prefix and a zero tail from the first
signal to make a modified first signal, transforming the modified
first signal in a first frequency domain signal, correlating the
first frequency domain signal with a complex-conjugated, Fourier
transformed root sequence to create a first inverse
Fourier-transform, and performing serial detection of the first
inverse Fourier-transform, using both a ZC root sequence detection
and a M-root sequence detection in series, in order to detect the
first preamble sequence.
[0023] In one embodiment, the detecting of the first preamble
sequence includes using a parallel processing detection including,
removing a first cyclic prefix and a zero tail from the first
signal to make a modified first signal, transforming the modified
first signal in a first frequency domain signal, correlating the
first frequency domain signal with a complex-conjugated, Fourier
transformed root sequence to create a first inverse
Fourier-transform, performing parallel detection of the first
inverse Fourier-transform, using both a ZC root sequence detection
and a M-root sequence detection in parallel, in order to detect the
first preamble sequence.
[0024] In one embodiment, the detecting of the first preamble
sequence includes a processing detection in a time domain that is
one of a serial processing detection and a parallel processing
detection, the processing detection in the time domain including a
direct correlation between the received signal and time domain
reference sequences.
[0025] At least another example embodiment is related to at least a
first network node in a communication network.
[0026] In one embodiment, the at least a first network node
includes at least one processor, configured to, generate a first
preamble sequence, the at least one processor being capable of
generating a first type of preamble sequence and a second type of
preamble sequence, transmit a first request message to a receiver
to request network resources, the first request message including
the first preamble sequence which is one of the first type of
preamble sequence and the second type of preamble sequence, and
receive a feedback message from the receiver, and control the
network data traffic of the communication network based on the
feedback message.
[0027] In one embodiment, the first request message includes a
first set of data payload packets associated with the first request
message, the at least one processor controlling the network data
traffic by being further configured to, transmit a second set of
data payload packets, using assigned network resources, following
the reception of the feedback message, the feedback message
identifying the assigned network resources.
[0028] In one embodiment, the first type of preamble sequence is a
cyclic-shifted Zadoff-Chu (ZC) root sequence, and the second type
of preamble sequence is a circular delay-Doppler shifted M-root
sequence.
[0029] In one embodiment, the at least one processor is further
configured to, receive, from the receiver, indicator information
indicating that the at least one processor should use one of the
first type of preamble sequence and the second type of preamble
sequence in order to generate the first preamble sequence.
[0030] At least another example embodiment relates to at least a
first network node in a communication network.
[0031] In one embodiment, the at least a first network node
includes at least one processor, configured to, receive a signal
from a transmitter, the signal including a first preamble sequence,
detect the first preamble sequence within the first signal, the at
least one processor being capable of detecting a first type of
preamble sequence and a second type of preamble sequence, identify
a first request message within the first signal based on the
detected first preamble sequence, and control the network data
traffic of the communication network based on the identified first
request message.
[0032] In one embodiment, the at least one processor identifies the
first request message by being further configured to identify a
first set of data payload packets within the first signal that is
associated with the first request message, and the at least one
processor controls the network data traffic by being further
configured to, transmit a feedback message, the feedback message
identifying assigned network resources, and receive a second set of
data payload packets using the assigned network resources.
[0033] In one embodiment, the first type of preamble sequence is a
cyclic-shifted Zadoff-Chu (ZC) root sequence, and the second type
of preamble sequence is a circular delay-Doppler shifted M-root
sequence.
[0034] In one embodiment, the at least one processor detects the
first preamble sequence by using a serial processing detection that
includes the at least one processor being configured to, remove a
first cyclic prefix and a zero tail from the first signal to make a
modified first signal, transform the modified first signal in a
first frequency domain signal, correlate the first frequency domain
signal with a complex-conjugated, Fourier transformed root sequence
to create a first inverse Fourier-transform, and perform serial
detection of the first inverse Fourier-transform, using both a ZC
root sequence detection and a M-root sequence detection in series,
in order to detect the first preamble sequence.
[0035] In one embodiment, the at least one processor detects the
first preamble sequence by using a parallel processing detection
that includes the at least one processor being configured to,
remove a first cyclic prefix and a zero tail from the first signal
to make a modified first signal, transform the modified first
signal in a first frequency domain signal, correlate the first
frequency domain signal with a complex-conjugated, Fourier
transformed root sequence to create a first inverse
Fourier-transform, perform parallel detection of the first inverse
Fourier-transform, using both a ZC root sequence detection and a
M-root sequence detection in parallel, in order to detect the first
preamble sequence.
[0036] In one embodiment, the at least one processor detects the
first preamble sequence by being further configured to, perform a
processing detection in a time domain that is one of a serial
processing detection and a parallel processing detection, the
processing detection in the time domain including a direct
correlation between the received signal and time domain reference
sequences.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The above and other features and advantages of example
embodiments will become more apparent by describing in detail,
example embodiments with reference to the attached drawings. The
accompanying drawings are intended to depict example embodiments
and should not be interpreted to limit the intended scope of the
claims. The accompanying drawings are not to be considered as drawn
to scale unless explicitly noted.
[0038] FIG. 1 illustrates a conventional network 10 with an
Internet Protocol (IP) Connectivity Access Network (IP-CAN) and an
IP Packet Data Network (IP-PDN);
[0039] FIG. 2 illustrates a conventional E-UTRAN Node B (eNB);
[0040] FIG. 3 illustrates a conventional network controller;
[0041] FIG. 4 illustrates a conventional user equipment (UE);
[0042] FIG. 5 illustrates a reconfigured E-UTRAN Node B (eNB), in
accordance with an example embodiment;
[0043] FIG. 6 illustrates a reconfigured network controller, in
accordance with an example embodiment;
[0044] FIG. 7 illustrates a reconfigured UE, in accordance with an
example embodiment;
[0045] FIG. 8 illustrates a method of preamble transmission to
control network traffic, in accordance with an example
embodiment;
[0046] FIG. 9 illustrates a method of preamble detection to control
network traffic, in accordance with an example embodiment;
[0047] FIG. 10 illustrates a method of preamble detection involving
a serial processing detection, in accordance with an example
embodiment; and
[0048] FIG. 11 illustrates a method of preamble detection involving
a parallel processing detection, in accordance with an example
embodiment.
DETAILED DESCRIPTION
[0049] While example embodiments are capable of various
modifications and alternative forms, embodiments thereof are shown
by way of example in the drawings and will herein be described in
detail. It should be understood, however, that there is no intent
to limit example embodiments to the particular forms disclosed, but
on the contrary, example embodiments are to cover all
modifications, equivalents, and alternatives falling within the
scope of the claims. Like numbers refer to like elements throughout
the description of the figures.
[0050] Before discussing example embodiments in more detail, it is
noted that some example embodiments are described as processes or
methods depicted as flowcharts. Although the flowcharts describe
the operations as sequential processes, many of the operations may
be performed in parallel, concurrently or simultaneously. In
addition, the order of operations may be re-arranged. The processes
may be terminated when their operations are completed, but may also
have additional steps not included in the figure. The processes may
correspond to methods, functions, procedures, subroutines,
subprograms, etc.
[0051] Methods discussed below, some of which are illustrated by
the flow charts, may be implemented by hardware, software,
firmware, middleware, microcode, hardware description languages, or
any combination thereof. When implemented in software, firmware,
middleware or microcode, field programmable gate array (FPGAs),
application specific integration circuit (ASICs), the program code
or code segments to perform the necessary tasks may be stored in a
machine or computer readable medium such as a storage medium, such
as a non-transitory storage medium. A processor(s) may perform
these necessary tasks.
[0052] Specific structural and functional details disclosed herein
are merely representative for purposes of describing example
embodiments. This invention may, however, be embodied in many
alternate forms and should not be construed as limited to only the
embodiments set forth herein.
[0053] It will be understood that, although the terms first,
second, etc. may be used herein to describe various elements, these
elements should not be limited by these terms. These terms are only
used to distinguish one element from another. For example, a first
element could be termed a second element, and, similarly, a second
element could be termed a first element, without departing from the
scope of example embodiments. As used herein, the term "and/or"
includes any and all combinations of one or more of the associated
listed items.
[0054] It will be understood that when an element is referred to as
being "connected" or "coupled" to another element, it can be
directly connected or coupled to the other element or intervening
elements may be present. In contrast, when an element is referred
to as being "directly connected" or "directly coupled" to another
element, there are no intervening elements present. Other words
used to describe the relationship between elements should be
interpreted in a like fashion (e.g., "between" versus "directly
between," "adjacent" versus "directly adjacent," etc.).
[0055] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
example embodiments. As used herein, the singular forms "a," "an"
and "the" are intended to include the plural forms as well, unless
the context clearly indicates otherwise. It will be further
understood that the terms "comprises," "comprising," "includes"
and/or "including," when used herein, specify the presence of
stated features, integers, steps, operations, elements and/or
components, but do not preclude the presence or addition of one or
more other features, integers, steps, operations, elements,
components and/or groups thereof.
[0056] It should also be noted that in some alternative
implementations, the functions/acts noted may occur out of the
order noted in the figures. For example, two figures shown in
succession may in fact be executed concurrently or may sometimes be
executed in the reverse order, depending upon the
functionality/acts involved.
[0057] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which example
embodiments belong. It will be further understood that terms, e.g.,
those defined in commonly used dictionaries, should be interpreted
as having a meaning that is consistent with their meaning in the
context of the relevant art and will not be interpreted in an
idealized or overly formal sense unless expressly so defined
herein.
[0058] Portions of the example embodiments and corresponding
detailed description are presented in terms of software, or
algorithms and symbolic representations of operation on data bits
within a computer memory. These descriptions and representations
are the ones by which those of ordinary skill in the art
effectively convey the substance of their work to others of
ordinary skill in the art. An algorithm, as the term is used here,
and as it is used generally, is conceived to be a self-consistent
sequence of steps leading to a desired result. The steps are those
requiring physical manipulations of physical quantities. Usually,
though not necessarily, these quantities take the form of optical,
electrical, or magnetic signals capable of being stored,
transferred, combined, compared, and otherwise manipulated. It has
proven convenient at times, principally for reasons of common
usage, to refer to these signals as bits, values, elements,
symbols, characters, terms, numbers, or the like.
[0059] In the following description, illustrative embodiments will
be described with reference to acts and symbolic representations of
operations (e.g., in the form of flowcharts) that may be
implemented as program modules or functional processes include
routines, programs, objects, components, data structures, etc.,
that perform particular tasks or implement particular abstract data
types and may be implemented using existing hardware at existing
network elements. Such existing hardware may include one or more
Central Processing Units (CPUs), digital signal processors (DSPs),
application-specific-integrated-circuits, field programmable gate
arrays (FPGAs) computers or the like.
[0060] It should be borne in mind, however, that all of these and
similar terms are to be associated with the appropriate physical
quantities and are merely convenient labels applied to these
quantities. Unless specifically stated otherwise, or as is apparent
from the discussion, terms such as "processing" or "computing" or
"calculating" or "determining" of "displaying" or the like, refer
to the action and processes of a computer system, or similar
electronic computing device, that manipulates and transforms data
represented as physical, electronic quantities within the computer
system's registers and memories into other data similarly
represented as physical quantities within the computer system
memories or registers or other such information storage,
transmission or display devices.
[0061] Note also that the software implemented aspects of the
example embodiments are typically encoded on some form of program
storage medium or implemented over some type of transmission
medium. The program storage medium may be any non-transitory
storage medium such as magnetic (e.g., a floppy disk or a hard
drive) or optical (e.g., a compact disk read only memory, or "CD
ROM"), and may be read only or random access. Similarly, the
transmission medium may be twisted wire pairs, coaxial cable,
optical fiber, or some other suitable transmission medium known to
the art. The example embodiments not limited by these aspects of
any given implementation.
[0062] Section 1--General Methodology:
[0063] It has been determined that the use of ZC-sequences may not
be optimal for all network communications. For example, a drawback
of ZC-sequences is a relatively high susceptibility against
frequency impairments, such as oscillator center-frequency offsets
(CFO) in a transmitter or receiver of the network 10, or mobility
induced Doppler shifts (especially if UEs 110 are traveling at
relatively moderate to higher speeds). Therefore, new sequences
with higher robustness against frequency impairments may be
beneficial in improving an overall system-performance of a network
while allowing for the use of low-cost devices that may have
relaxed oscillator requirements. M-sequences, with a circular
delay-Doppler shift, may offer enhanced properties, especially with
regard to center-frequency offsets (CFOs), and especially with
regard to future radio systems such as 5G networks.
[0064] In particular, M-sequences may provide a higher resistance
against frequency uncertainties, especially for applications in
high-speed and high carrier-frequency scenarios, and within 5G
networks. Specifically, M-sequences may be less susceptible to
frequency uncertainties, as compared to legacy ZC-sequences. The
use of M-sequences can especially be implemented in scenarios with
higher UE 110 mobility, without a need to introduce restricted
preamble sets, as required for ZC-sequences.
[0065] The use of new types of sequences may provide more reliable
service for UEs 110 as compared to the use of legacy ZC-sequences,
only. Low-cost terminals may cause a relative center-frequency
offset, where an M-sequence may perform significantly better at an
initial access rate, as compared to the ZC-sequences. Furthermore,
M-sequences achieve very small minimum final NACK rates, even in
presence of large frequency offsets. This property makes the use of
M-sequences attractive for ultra-reliable and low-latency
communication (URLLC) use cases.
[0066] It has been determined that the use of ZC- and M-sequences
may coexist in the same time and frequency physical resources,
where the system performance does not degrade in the presence of
dual sequence (or, multi-sequence) types. A feature of a
multi-sequence type system may be that the baseband processing may
be accomplished without greatly disrupting legacy network systems.
At a transmitter (UE 110) side, the device may be enabled to
generate new preambles. Because preambles may be generated in a
digital domain, it may be possible to cause the processor of the
transmitter to be reconfigured to use multiple sequence types (such
as ZC- and M-sequences). At the receiver (eNB 105) side, a
controller of the eNB 105 may be reconfigured to perform
correlations with both the legacy ZC-sequence, as well as the
M-sequence. These correlations at the eNB 105 may either be
performed in a parallel or serial arrangement. Therefore, the
provisioning of additional sequences (such as M-sequences) for use
in PRACH preamble generation may be greatly beneficial to improving
the performance of expanding network systems.
[0067] The new sequences may be derived by circular delay-Doppler
(time-frequency) shifts of m-sequences. These sequences show a
higher robustness against frequency impairments, and a
significantly reduced false-alarm probability, as compared to
legacy ZC-sequences. In addition, more sequences may be uniquely
detected at an eNB 105. Important key-performance metrics, such as
protocol latencies, upload probabilities and/or cell-coverage, may
therefore be significantly improved.
[0068] Section 2--Preamble Sequence Generation and Properties:
[0069] Section 2.1--Design of Zadoff-Chu Sequences
[0070] In an uplink random access preamble sequence, for use in a
network such as a long-term evolution (LTE) network, the sequence
may be generated from root Zadoff-Chu sequences, which may defined
as follows.
x u [ n ] = e - j .pi. un ( n + 1 ) N , 0 .ltoreq. n .ltoreq. N - 1
Equation 1 ##EQU00001##
[0071] A prime sequence length may be denoted as "N," and the
physical root may be denoted as "u." For LTE, the sequence length N
may be 839, and the physical root index may range from 1 to 838.
Its value may depend on a broadcasted logical root sequence index
and a mapping (that is defined by 3GPP TS 36.211, "Physical
channels and modulation"). Usually, different physical root indices
may be assigned to neighbor cells in order to guarantee low
cross-correlations between preambles.
[0072] Different preamble sequences from one root sequence may be
generated by applying cyclic shifts.
x.sub.u,v[n]=x.sub.u[(n+C.sub.p)mod N] Equation 2
[0073] Where the cyclic shift C.sub.v may be given by multiples of
the distance N.sub.CS between two preambles.
C v = { vN CS v = 0 , 1 , N N CS - 1 , N CS .noteq. 0 0 N CS = 0
Equation 3 ##EQU00002##
[0074] Section 2.2 Design of Circular Delay-Doppler Shifted
m-Sequences
[0075] An m-sequence may be generated via linear-feedback shift
registers. Sequences that originate from a 10.sup.th order pseudo
noise (pn) generator may be determined, where a generator
polynomial may be defined as follows.
g(D)=D.sup.10+D.sup.9+D.sup.8+D.sup.5+D.sup.1+1 Equation 4
[0076] An output of the generator may be a binary sequence b(n) of
length 1023 that may be transformed into a BPSK (.+-.1) modulated
base sequence x[n]. Different base sequences may be generated by
initializing the pn-generator with different values (e.g. from cell
IDs). Alternatively, a cell-specific base offset may be introduced.
From a base sequence, different preamble sequences may be derived
by applying circular delay-Doppler shifts (as defined for instance
by J. C., Guey "The design and detection of signature sequences in
time-frequency selective channel," IEEE 19th International
Symposium on Personal, Indoor and Mobile Radio Communications,
2008), as follows.
x u , v [ n ] = x [ ( n - C v ) mod N ] e j 2 .pi. fun N , 0
.ltoreq. n .ltoreq. N - 1 Equation 5 ##EQU00003##
[0077] Where C.sub.v may be the cyclic shift defined as an integer
multiple of N.sub.CS. Here, the N.sub.CS value may adjust the
separability in time domain and should be therefore larger than the
maximum expected delay spread. The phase signature parameter f may
be selected larger than the maximum expected Doppler spread in the
system. The cell ID may be used as a root index parameter u in
order to guarantee that neighbor cells show different frequency
shifts.
[0078] Section 2.3 Correlation Properties:
[0079] Ambiguity functions (AF) (as defined for instance by H. He
et. al., "Waveform Design for Active Sensing Systems," Cambridge
University Press, 2012) are well-known and often employed in radar
technology to analyze an auto- and cross correlation of a reference
signal with delay-Doppler (.tau., .nu.) shifted versions of the
same or a different signal. The periodic auto-ambiguity function
(PAF) may be defined as follows.
.chi. ( .tau. , v ) = 1 T .intg. 0 T u ( t ) u * ( t - .tau. ) e -
j 2 .pi. v ( t - .tau. ) dt ##EQU00004##
[0080] And the periodic cross-ambiguity function may be defined as
follows.
.chi. ( .tau. , v ) = 1 T .intg. 0 T u ( t ) w * ( t - .tau. ) e -
j 2 .pi. v ( t - .tau. ) dt ##EQU00005##
[0081] In a real-world system application, an absolute value of the
ambiguity function may be considered as an output of a preamble
correlator. That is to say, a correlation may be calculated for the
AF between an unmodified expected signal and a signal that
experienced delays due to multipath propagation and Doppler-effect
induced frequency shifts due to the terminal's mobility or offsets
in the transmitter's or receiver's oscillator. Therefore, the AF
may be known to be a good measure to characterize a sequence's
ability to be uniquely identified in a time-frequency dispersive
channel.
[0082] Section 2.3.1--Ambiguity Function of Zadoff-Chu
Sequences:
[0083] The PAF for a ZC sequence of length 31 is briefly discussed,
herein. In the following we briefly discuss the PAF for a ZC
sequence of length 31. In absence of a frequency shift .nu.=0, a
correlation is found to be a maximum at .tau.=0 and zero for
.tau..noteq.0. This property had been a motivation to use
Zadoff-Chu sequences as preamble sequence for the RACH. However, in
the presence of frequency shift, this may no longer the case.
Specifically, additional correlation peaks occur for specific
frequency and time shifts. These self-images of the original
transmitted sequence may result in detection errors at the
receiver. For example: Assume that the sequence, transmitted with
zero time-frequency shift, experiences a Doppler shift by .nu.=+1
(corresponding to one subcarrier spacing), then the correlation
based receiver may detect a sequence at around .tau.=10. The
receiver will therefore wrongly interpret a detected sequence as
one that has been transmitted with a cyclic time shift equivalent
to .tau.=10. Actually, in this scenario there may be two errors.
Firstly, the receiver may not able to detect the transmitted
sequence (i.e., there may be a mis-detection event). Secondly, the
receiver may observe a sequence that likely had not been
transmitted by any terminal within the cell (i.e., there may be a
false-alarm event). A collision may occur if a second terminal in
the same cell transmits a preamble with a cyclic shift equal
.tau.=10 without frequency uncertainty. A standardized method to
resolve ambiguity is to introduce restricted sets (as defined in
3GPP TS 36.211, "Physical channels and modulation"). A drawback of
this approach may be that a substantial number of preambles may not
be available anymore.
[0084] Section 2.3.2--Ambiguity Function of Delay-Doppler Shifted
M-Sequences:
[0085] In investigating an absolute value of the periodic
auto-ambiguity function (PAF) as function of time-frequency shifted
versions of a delay-Doppler shifted m-sequence, the relationship
displays almost ideal correlation behavior. This means that it may
be expected that false alarm errors may be substantially reduced.
Additionally, significant increases in robustness against frequency
impairments are also provided and more preambles may be used within
a cell.
[0086] Section 2.4--Peak-to-Average Power Ratio (PAPR):
[0087] The peak-to-peak ratio (PAPR) for the M-sequences may be
worse than for ZC-Sequences. For a sequence length around 1024, the
difference may be about 3 dB.
[0088] Section 2.5--Baseband Signal Generation:
[0089] For both the ZC-sequences and the delay-Doppler shifted
m-sequences, a baseband generation may follow procedures defined
within LTE networks. Firstly, the sequence x.sub.u,v[n] may be
transformed into a frequency domain via a N point DFT. The mapping
onto the subcarriers and finally the signal in time domain may be
generated via an IDFT.
[0090] Section 2.6--Receiver Design Considerations:
[0091] On a receiver side (eNB 105), a preamble correlation
function may be extended to support a new sequence type (such as
the m-sequence). Specifically, a newly introduced root sequence may
be added to the ZC root sequences to be capable of determining
sequences derived from multiple root sequences. Multi-root
detection may be conducted in a parallel or serial arrangement (as
described below in more detail), depending on the preamble detector
design.
[0092] Section 3--Performance Assessment Via
System-Simulations:
[0093] Section 3.1--Radio Access Protocol:
[0094] Simulations have been performed to assess a value of cyclic
delay-Doppler shifted sequences for random access. Assumptions may
be based on the standard 3GPP 38.913 v.0.3.1, "Study on Scenarios
and Requirements for Next Generation Access Technologies" (Release
14, June 2016).
[0095] The uplink direction of a system may be dedicated to the
transmission of IoT sensor or actuator traffic. 10 MHz of bandwidth
may be assumed and a resource structure that may be equal to that
of LTE (i.e. 50 Physical Resource Blocks (PRBs)) may each consist
of 12 subcarriers and 14 OFDM symbols. Although 50 PRBs may be
available, only 48 may be used for small packet access. Three OFDM
symbols may be used for pilots and sounding leaving 11.times.12=132
resource elements per PRB for data.
[0096] A two-stage access with pooled resources (as described in
Stephan Saur, Andreas Weber, and Gerhard Schreiber "Radio Access
Protocols and Preamble Design for Machine Type Communications in
5G," in Proc. Forty-Ninth Asilomar Conference on Signals, Systems
and Computers, Pacific Grove, Calif., p. 8-12, November 2015) may
be selected as an access procedure. The PRBs in one subframe may be
subdivided into a number of "short-packet blocks (SPBs)." One block
may be dedicated to resource requests over PRACH, while six SPBs
may be dedicated to data transmission. Due to the total number of
48 PRB used for small packet transmission, the data resources may
have a size of 7 PRBs, while the request resource may have a size
of 6 PRBs. A short packet may consist of 840 data bits. QPSK may be
assumed for the modulation scheme, so that there is a code rate of
840/(11.times.12.times.7.times.2)=0.45 for the short packet
transmission.
[0097] Specific Implementation of an Example Method:
[0098] FIG. 5 illustrates a reconfigured E-UTRAN Node B (eNB) 105a,
in accordance with an example embodiment. In particular, eNB 105
may be reconfigured to include a preamble reception routine (PRR)
212 that may be saved in memory 225. Specifically, the PRR 212 may
provide instructions that may cause the processor 210 to perform
some or all of the method steps that are described below in
association with the method flowcharts depicted in FIGS. 9-11.
[0099] FIG. 6 illustrates a reconfigured network controller 300a,
in accordance with an example embodiment. In particular, CO 300a
may be reconfigured to include a preamble reception routine (PRR)
310 that may be saved in memory 304. Specifically, the PRR 310 may
provide instructions that may cause the processor 302 of the CO
300a, and/or the processor 210 of the eNB 105a, to perform some or
all of the method steps that are described below in association
with the method flowcharts depicted in FIGS. 8-11. Specifically,
the PRR 310 may provide instructions to either or both of the
processors 210/302, in order to cause either the CO 300a, or the
eNB 105a, or a combination of the CO 300a/eNB 105a to collectively
perform the receiver-side method steps of FIGS. 9-11, as described
below in more detail.
[0100] FIG. 7 illustrates a reconfigured UE 100a, in accordance
with an example embodiment. In particular, UE 100a may be
reconfigured to include a preamble transmission routine (PTR) 156
that may be saved in memory 150. Specifically, the PTR 156 may
provide instructions that may cause the processor 154 of the UE
100a to perform the transmitter-side method steps outlined in FIG.
8, as described below in more detail.
[0101] FIG. 8 illustrates a method of preamble transmission to
control network traffic, in accordance with an example embodiment.
The method steps may be accomplished by the processor 154 of UE
100a, where the PTR 156 provides the instructions for the processor
154 to perform these steps.
[0102] In step S400, the processor 154 may generate a preamble
sequence to be sent in a signal to the eNB 105a. The generation of
the preamble sequence may be accomplished unilaterally by the UE
100a, from the standpoint that the processor 154 may determine the
sequence-type that is to be used to generate the sequence.
Alternatively, the eNB 105a (or the CO 300a) may send indicator
information to the UE 100a in order to instruct the processor 154
as to which sequence-type the processor 154 is to use to generate a
preamble sequence. Specifically, the preamble sequence may be, for
instance, either a ZC-sequence or a cyclic delay-Doppler shifted
M-sequence (as an example).
[0103] Such indicator information may be part of information
broadcasted by the eNB 105a to the UE 100a, e.g. via a Broadcast
Control Channel (BCCH) in LTE. In case of a preamble sequence for
use in PRACH, the indicator information may be defined in the
information element PRACH-Config transmitted as part of System
Information Block 2 in LTE (see 3GPP TS 36.331 "Evolved Universal
Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC);
Protocol specification"). In particular, the PRACH-ConfigSIB may be
defined with an additional sequence capability parameter in the
following way:
TABLE-US-00001 PRACH-ConfigSIB ::= SEQUENCE { rootSequenceIndex
INTEGER (0..837), prach-ConfigInfo PRACH-ConfigInfo
prach-SequenceCapability ENUMERATED (st1,st2,st3)
[0104] The sequence capability parameter describes the basestation
processing capabilities on PRACH. The mapping between the
enumeration value and the capabilities may be implemented in
different ways. For example, if one bit of information is employed,
an enumeration value with value st1 could indicate that only ZC-
(or legacy) preamble sequences may be processed by the base
station. An enumeration value with value st2 could then indicate
that the base station has the capability to process further (legacy
plus advanced) preamble sequences, e.g. m-sequences. UEs with a
capability to generate both legacy and advanced preamble sequences
may then determine the sequence-type that is to be used to generate
the sequence. Alternatively, if two bits of information are
employed, a first enumeration value, (e.g. st1) could be used to
indicate that the base station solely has the capability to process
legacy sequences, e.g. ZC-sequences, a second enumeration value
(e.g. st2) could be used to indicate that the base station solely
has the capability to process advanced sequences, e.g. M-sequences,
and a third enumeration value (e.g. st3) could be used to indicate
that the base station has the capability to process both legacy and
advanced sequences. It will be understood that the sequence
capability parameter may not indicate the intrinsic capability of
the base station, but instead may indicate the base station
configuration in this regard. That is, if the base station is
capable of handling both legacy and advanced sequences, but for
some reason has chosen to process one type of preamble sequence,
this choice may be reflected by the sequence capability
parameter.
[0105] Alternatively, the indicator information in case of PRACH,
could be part of the PRACH-ConfigInfo information structure. In yet
another implementation, the indicator information in case of PRACH
may be part of another PRACH-related information structure, for
example RACH-ConfigCommon (see 3GPP TS 36.331 "Evolved Universal
Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC);
Protocol specification").
[0106] In step S402, the processor 154 may transmit a request
message to the eNB 105a. The request message may include the
preamble sequence. Specifically, the request message may include
either the ZC-sequence, or a cyclic delay-Doppler shifted
M-sequence (as an example), and the request message does not need
to contain any further information about the requesting UE 100a.
That is to say, the UE 110a may randomly choose one out of the
offered preamble-types in the cell of the network 10. The request
message may also include a first set of data payload packets that
may be appended to the preamble sequence. Or, the first set of data
payload packets may otherwise be transmitted in conjunction with
the request message that include the preamble sequence.
[0107] In step S404, the processor 154 may receive a feedback
message from the eNB 105a (or from the CO 300a). Specifically,
after the UE 100a initially transmits the request message, the
processor 154 may wait for a specified number of sub-frames for the
feedback message to be received. The feedback message, e.g. similar
or identical to a Random Access Response message received on a
PDSCH or PDCCH channel in LTE (for instance), may contain
information on available or attributed network resources (for
instance, attributed physical resource blocks,
modulation-and-coding scheme or random access preamble identifier)
that the UE 100a may then use to send and receive data payload
packets with the eNB 105a and/or CO 300a.
[0108] In step S406, the processor 154 may then cause the UE 100a
to transmit at least a second set of data payload packets to the
eNB 105a. Upon receiving an acknowledgement (ACK) signal from eNB
105a, the processor 154 will cease to attempt to re-send the second
set of data payload packets. Otherwise, the processor 154 will
continue to attempt to re-send the second set of data payload
packets, until an ACK message is received from the eNB 105a or,
alternatively, until a predetermined number of attempts has been
reached. Upon receipt of a negative-acknowledgment (NACK), or upon
exceeding the maximum number of re-send attempts, the processor 154
will, with a random backoff delay, reinitiate access with the eNB
105a (where the number of trials may be set to 4, for
instance).
[0109] FIG. 9 illustrates a method of preamble detection to control
network traffic, in accordance with an example embodiment. The
method steps may be accomplished by the processor 210 of eNB 105a,
or processor 302 of CO 300a, or a combination of the processors
210/302, where the PRR 212 and/or PRR 310 may provide the
instructions for the processors 210/302 to perform these steps.
While the description (below) indicates that the processor 210 of
the eNB 105a performs these steps, it should be understood that the
processor 302 of the CO 300a may share some of the method step
responsibilities.
[0110] In step S500, the processor 210 may receive a signal from
the UE 100a. the signal may include a preamble sequence, where the
preamble sequence may be one of a number of types of preamble
sequences. Optionally, the processor 210 of the eNB 105a may
initially command the UE 100a to use a particular type of preamble
sequence, such that the eNB 105a (or the CO 300a) may dictate the
preamble sequence-type. For PRACH this may be done in a way as
described previously with reference to FIG. 8. Otherwise, the
processor 154 of the UE 100a may unilaterally determine the
sequence type.
[0111] In step S502, the processor 210 may detect the preamble
sequence within the signal.
[0112] In step S502, the processor 210 may identify a request
message within the first signal based on the detected preamble
sequence. The request message may include a first set of data
payload packets that may be appended to, or otherwise transmitted
in conjunction with, the preamble sequence with the request
message.
[0113] In step S506, the processor 210 may transmit a feedback
message. The feedback message, e.g. similar or identical to a
Random Access Response message transmitted on a PDSCH or PDCCH
channel in LTE (for instance), may contain information on available
or attributed network resources (for instance, attributed physical
resource blocks, modulation-and-coding scheme or random access
preamble identifier) that the UE 100a may then use to send and
receive data payload packets with the eNB 105a (and/or CO
300a).
[0114] In step S508, the processor 210 may receive a second set of
data payload packets from the UE 100a, in response to the feedback
message. The processor 210 may then send an acknowledgement (ACK)
to the UE 100a, acknowledging receipt of the second set of payload
packets. Otherwise, in the event that the processor 210 does not
receive a second set of data payload packets, the processor 210 may
send a negative-acknowledgement (NACK) message to the UE 100a,
indicating that payload packets were not received by the eNB 105a
following the transmission of the feedback message.
[0115] Preamble Detection:
[0116] The processor 210 of the eNB 105a may be able to detect that
a certain preamble is used, even in instances when the UE 100a
unilaterally determines the preamble-type for the preamble
sequence. A Forward Consecutive Mean Excision (FCME) algorithm may
be used for the purpose of preamble signature detection (as
disclosed in J. Vartiainen et. al., "False Alarm Rate Analysis of
the FCME Algorithm in Cognitive Radio Applications," AICT 2015, the
Eleventh Advanced International Conference on Telecommunications).
However, the processor 210 of the eNB 105a may not be capable of
detecting if there is a collision on the considered preamble (just
as the processor 302 of the CO 300a would also be unable to provide
such a detection of a collision).
[0117] It should be noted that resource requests may contain
false-alarm requests. That is to say, it may be possible for
physical resources to be attributed to a request, but there is not
a UE 100a that will ultimately use the resources for data
transmission (i.e., a false alarm might be a reason for resource
blocking).
[0118] Preamble Detector Design:
[0119] FIG. 10 illustrates a method of preamble detection involving
a serial processing detection, in accordance with an example
embodiment. This scheme may allow for simultaneous detection of
both ZC- and M-preamble sequences, that may be transmitted over the
same time-frequency resources, where the detection may occur in a
serial processing chain (whereas a parallel processing chain may
alternatively be used instead, as described in relation to FIG.
11).
[0120] In a serial arrangement, detection of ZC and M-sequences may
be performed by sharing a same processing resources in a time
domain. That is to say, within one processing cycle, the sequences
derived from one root sequence (either ZC or M-root sequence) may
be detected. As shown in FIG. 10, in step S600, the processor 210
of the eNB 105a may first remove a cyclic prefix and a zero tail of
the received digital signal from the UE 100a, in order to create a
modified signal.
[0121] In step S602, the processor 210 may transform the modified
signal, which is a time domain signal, in order to produce a
frequency domain signal, e.g. by means of a Discrete Fourier
Transform (DFT).
[0122] In step S604, the processor 210 may correlate the frequency
domain signal, after subcarrier-demapping, using a
complex-conjugated, Fourier transformed root-sequence, in order to
create a Fourier-transformed signal.
[0123] In step S606, the processor 210 may use a subsequent inverse
Fourier-transform to detect either ZC- or M-sequence type preamble
sequences (where this detection is accomplished in series, starting
with a first detection of a ZC-Sequence, followed secondly by a
detection of an M-sequence or vice versa) in order to deliver a
power-delay spectrum that is then input for the signature detection
unit. Power-delay spectra from other antenna ports may be combined
before signature detection. An advantage of a serial arrangement is
that, only one processing chain may be required for preamble
detection. A drawback of this serial detection approach (as
compared to a parallel detection scheme, described in FIG. 11), is
that it may result in an extra delay time.
[0124] FIG. 11 illustrates a method of preamble detection involving
a parallel processing detection, in accordance with an example
embodiment. In a parallel processing arrangement, detection of ZC
and M-sequences may be performed by having redundant (i.e.,
dedicated) processing resources in a time domain, where each
processing resource may individually detect one type of preamble
sequence (such as ZC- and M-sequence type preambles). As shown in
FIG. 11, in step S700, the processor 210 of the eNB 105a may first
remove a cyclic prefix and a zero tail of the received digital
signal from the UE 100a, in order to create a modified signal.
[0125] In step S702, the processor 210 may transform the modified
signal, which is a time domain signal, in order to produce a
frequency domain signal, e.g. by means of a Discrete Fourier
Transform (DFT).
[0126] In step S704, the processor 210 may correlate the frequency
domain signal, after subcarrier-demapping, using a
complex-conjugated, Fourier transformed root-sequence, in order to
create a Fourier-transformed signal.
[0127] In step S706, the processor 210 may use the subsequent
inverse Fourier-transform to detect either ZC- or M-sequence type
preamble sequences in order to deliver a power-delay spectrum that
is then input for the signature detection unit, where the detection
of the different types of sequences is each conducted at a same
time (i.e., in parallel).
[0128] A potential disadvantage of a parallel scheme (as compared
to a series scheme) is that this approach may have a somewhat
higher implementation effort. An advantage of this scheme is that
the scheme offers fewer delays than the serial detection.
[0129] Results:
[0130] In order to compare between conventional ZC-sequences, as
compared to the use of M-sequences, investigations included the use
of ZC sequences having a length of 1021. The M-sequences were used
with a length of 1023. A transmission bandwidth was used over 6
PRBs in accordance to LTE. The following three metrics were
investigated as key-performance metrics.
[0131] False alarm probability: A ratio between a total number of
false alarms and a total number of possible transmitted
preambles.
[0132] Final NACK probability: A ratio between a total number of
UEs 100a that give up access or data transmission after the
4.sup.th failed trial, and a total number of initial access
attempts.
[0133] Delay: An average required time from initial access over
PRACH until successful transmission of a data packet (metric
includes all retrials).
[0134] Case 1: In a first implementation, a scenario with 64
preambles per cell was considered. The preambles were derived from
one root sequence. Key performance indicators between ZC- and
M-Sequences were compared as function of the initial access rate
and center-frequency offset (CFO).
[0135] A false alarm rate was constantly small for the cyclic
delay-Doppler shifted M-sequences. Even in the presence of
significant center-frequency offsets, an observed error rate was
significantly smaller than 1%. In contrast ZC-sequences show good
false alarm rates only for the case without frequency offset.
Typically, the new type of sequences showed a factor 10-100 smaller
false alarm rates than traditional ZC-sequences. This behavior
appeared to be a direct consequence of the improved correlation
properties in the 2-dimensional time-frequency plane of M-sequences
against ZC-sequences.
[0136] With regard to a final NACK rate, it was also assumed that a
system target final NACK probability was set to 1%, and a relative
center-frequency offset was set equal 0.25. The ZC-sequences were
able to support a maximum initial access rate of 3500 attempts per
second and sector. In contrast, the M-sequences allowed a maximum
initial rate of up to 5100 attempts per second and sector. Based on
this information, a maximum number of supported devices per area is
approximately 4.8 Million devices/km.sup.2 for the ZC-sequences,
and 7.3 Million devices/km.sup.2 for the M-sequence case. In this
calculation, it was assumed that an initial access rate of 1 packet
per 100 s per device. The example embodiment preamble design may
can offer service to significantly more UEs 100a, based on the
trials. Specifically, with regard to the use of ultra-low cost
transmitters with relaxed requirements on the oscillators, the
trials of the example embodiments indicated superior performance
over the use of ZC-sequence preambles, only.
[0137] With regard to protocol delay, in the presence of frequency
impairments, it was observed for the ZC-sequence that a degradation
of the protocol delays was experienced with an increase in initial
access rate. In contrast, the use of the M-sequences does not cause
delay degradation, even in presence of high frequency offsets.
[0138] Case 2: In a second investigation, a scenario was considered
with different number of offered preambles in a cell. All preambles
were derived from one root sequence. The relative center frequency
offset was 0.25.
[0139] With regard to false alarm rates, it was observed that
additional offered sequences increase a probability for false
alarms, but this is much more relevant for ZC-sequences, as
compared to M-sequences. For example, increasing a number of
sequences from 64 to 128 increases a false alarm rate by about 0.1%
when using M-sequence, whereas the alarm rate increased by about
2-3% when using the ZC-sequence.
[0140] With regard to a final NACK rate, it was assumed that a 1%
target final NACK probability was desired. For the cyclic
delay-Doppler shifted M-sequences, it was observed that a small
improvement in the maximum number of served mobiles was
experienced, if the number of offered preambles was increased from
64 to 128. In contrast for the ZC-sequence, it was observed that a
significant reduction in a number of served mobiles occurred (i.e.
from 3500 initial attempts per second to only 1000 initial attempts
per second).
[0141] With regard to protocol delay, a delay degradation for the
M-sequences was observed to be small, regardless of how many
preambles that were offered in a cell. On the other hand,
ZC-sequences show a strong increase in delay figures with an
increasing number of offered preambles.
[0142] Example embodiments having thus been described, it will be
obvious that the same may be varied in many ways. Such variations
are not to be regarded as a departure from the intended spirit and
scope of example embodiments, and all such modifications as would
be obvious to one skilled in the art are intended to be included
within the scope of the following claims.
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